How to easily cache single AR object?

rubyonrails-talk
1

Hi,

I got a mailer that uses dynamic stylesheets, so when creating an email I'm doing Style.find_by_name("newsletter").

The problem is that it's fetching the same Style record for each email it creates and when sending newsletters there can be a lot of them. I could simply fetch this record in controller and just pass it as a parameter for deliver_email method, but it doesn't seem right for me - I'd like to keep as much as possible inside mailer class.

I can't also simply put STYLE = Style.find_by_name("newsletter") into Mailer class, because if admin changes the style, the mailer would still use cached object.

Is there a *simple* way to do it? This Style object can only be updated - it can't be destroyed. I'm using Rails 2.1.1.

2

If you dont want to get into memcache or other complex solutions you can do something simple like this:

class StylesCache   include Singleton

  def self.by_name(name)     self.instance.by_name(name)   end

  def by_name(name)     return @active_style if @active_style && @active_style.name == name

    @active_style = Style.find_by_name(name)     return @active_style   end end

style = StylesCache.by_name("newsletter")

3

Thanks for the answer, but I needed a way to clear the "cache" after the cached object was updated.

Finally made it like this:

class NewsletterMailer   def self.style     @@style ||= fetch_style   end   def self.reload_style     @@style = fetch_style   end end

and I'm calling NewsletterMailer.reload_style in Style#after_update callback.